The invention relates to a lockable caster wheel, in particular for movable hospital beds, with a fastening pin; a swivel arm, which can be swivelled around the fastening pin in a swivel bearing; a mechanism for fixing the swivelling motion of the swivel arm and at least one rotatable wheel, moreover with a tiltable brake lever to block the rotation of the wheel, and a locking bolt that is arranged coaxially to the fastening pin and, relative to said pin, can be moved in the axial direction against the action of a spring and that locks the swivel arm as a function of its axial position and/or blocks the wheel by means of the brake lever.
Such a caster wheel is known from the DE-OS No. 36 02 916. The fastening pin serves the purpose of mounting the caster wheel to a tubular foot, for example a hospital bed. In the prior art caster wheel the locking bolt can be moved axially but due to its hexagonal cross section, cannot be rotated in the fastening pin. At its bottom end the locking bolt has a disk washer that is moulded on and that has on its bottom side a toothing. A wheel fork that can be swivelled around the fastening pin guides a rotatable wheel. A brake arm can be swivelled below the back of this wheel fork. The toothing at the disk washer of the locking bolt can be meshed with a tooth segment that is fastened to the brake arm. If the locking bolt is forced into its bottom end position opposite the action of a compression spring by means of a cam disk, the toothing of the disk washer meshes with the tooth segment of the brake arm and presses it firmly on the tread on the wheel. In addition to the braking of the wheel, this meshing of the toothing also enables the blocking of the adjusted swivel position of the wheel fork with respect to the fastening pin. In this manner, the wheel is blocked from both swivelling and rotating. If the locking bolt is under the pressure of the compression spring in its upper end position, the wheel for locks in a snap-in position, which corresponds to setting the wheel straight ahead. This ability to fix the direction is especially advantageous for movable hospital bed in order to be able to move them straight ahead for long distances without having the wheels swivel in an undesired manner. If the locking bolt is located in an intermediate position between the bottom and upper end position, the wheel can be rotated freely and the wheel fork can be swivelled unimpeded around the fastening pin. The bed can then be moved freely in all conceivable directions.
The drawback with the prior art caster wheels that can be locked with respect to the swivel and rotary motion of the wheel is that they cannot absorb shocks. However, especially in the case of hospital beds there is a need to use an elastic caster wheel to absorb shocks from uneven surfaces when moving over said surfaces.
From the DE-OS No. 36 12 925 an elastic caster wheel is already known that has a swivelling swivel fork, a wheel fork, which can be tilted therein parallel to the axis of the roller wheel, for the caster roller wheel and a wheel fork spring that is arranged between said caster roller wheel and the swivel fork. The prior art caster wheel can absorb shocks but it offers no possibility of locking the swivel motion and/or blocking its rotation.